The present invention relates to a valve train of an internal combustion engine with a double camshaft.
A rotary drive that is specifically made for an adjusting shaft of a variable valve train is known from EP 1 347 154 A2 (Applicant: Hydraulik-Ring GmbH; Priority date: Mar. 20, 2003). A first rotatory hydraulic drive is joined to a second rotatory hydraulic drive so that coarse and fine adjustments of an exact cam position within a valve train chain are possible. In other words, the rotary angle position to be adjusted is made possible by a two-stage system.
U.S. Pat. No. 2,911,956 (Applicant: Smith; Date filed: Jan. 7, 1959) describes a plate-type positioner, by means of which a pivoting movement of a first plate influences the pivoting range of a second plate, and so forth.
WO 01/12996 A1 (Applicant: Raikamo; Priority date: Aug. 17, 1999) shows in FIG. 5a a two-stator shaft adjusting system, in which the rotor is limited in its pivoting range by the rotation of a first and a second stator.
One skilled in the art can derive from U.S. Pat. No. 5,233,948 (Applicant: Ford Motor Corporation; Date filed: Dec. 10, 1992) the advantages that can be found if the cams of superimposed camshafts can be adjusted relative to one another. Thus there has been the desire for several years to create valve trains that are configured so that they can individually control the events of several gas-exchange valves of a combustion chamber. The theoretical advantages can be derived from the Ford patent, but there is a lack of transferring these advantages to concrete proposals. By this reference, the principles theoretically disclosed in the Ford patent will apply as incorporated to the full extent in the present description of the invention.
Approaches for executing the teaching of U.S. Pat. No. 5,233,948 are known from FIGS. 4A to 4C of U.S. Pat. No. 5,235,939 (Applicant: Ford Motor Company; Date filed: Nov. 5, 1992), which illustrate a coaxial double camshaft with at least two sets of cams offset at an angle relative to one another, the cams of which are attached by fastening pins and fastening springs to the particular camshafts bearing them. A similar arrangement is known from WO 2005/040562 A1 (Applicant: Audi AG; Priority date: Oct. 25, 2003). According to the description, the position of the cams will be adjusted with hydraulic linear cylinders. A similar construction is known from FIG. 1 of DE 43 32 868 A1 (Applicant: BMW AG; Date filed: Sep. 27, 1993), which will also adjust the cam position of an intake cam to an exhaust cam by a linear movement. The representation in EP 0 397 540 A1 (Applicant: Regie Nationale des Usines Renault; Priority date: Mar. 17, 1989) also shows a linear-adjustable camshaft arrangement. A contour-fitted run-in pin, which influences via its surface the angular distance between two cams and thus the relative positions of the camshafts associated with these is known from FIGS. 5 and 6 of U.S. Pat. No. 4,332,222 (Applicant: Volkswagen AG; Priority date: May 20, 1978). Two hollow-shaft camshafts that engage in one another can be adjusted in their angular position relative to one another via a planetary gear with lengthwise holes according to the unexamined German application DE 36 24 827 A1 (Applicant: Süddeutsche Kolbenbolzenfabrik GmbH; Date filed: Jul. 23, 1986). In order to conform to present exhaust limit values in high-compression internal combustion engines, however, the outer shaft must also be adjustable relative to the drive shaft, particularly the crankshaft. Another basic concept for the creation of a nested cam contour can be derived from DE 199 14 909 A1 (Applicant: BMW AG; Date filed: Apr. 1, 1999). The cam contour of the principal cam of a camshaft can be widened with an auxiliary cam, in order to control the associated gas-exchange valve a second time, offset in time relative to the main event, and to thus make possible a boosting of the ejection or another ejection from the cylinder.
Another operating mode of a camshaft with adjustable double cam events is described in DE 10 2004 023 451 A1 (Applicant: General Motors Corp.; Priority date: May 16, 2003). Finally, the following two publications will be named: JP 11 17 31 20 (Applicant: Mitsubishi Motors Corp; Date filed: Dec. 8, 1997) and WO 1992/012 333 (Applicant: Porsche AG; Priority date: Jan. 12, 1991).
In summary, it can be seen that the following has been considered for many years: How can events in the gas-exchange valve train that are offset in time relative to one another be made adjustable in their phase positions?
DE 10 2005 014 680 A1 (Applicant: Mahle International GmbH, Priority date: Feb. 3, 2005) shows in several graphic representations a double camshaft that is equipped with a connected, grooved oil delivery unit in order to be able to further conduct the hydraulic oil to a hydraulic adjuster, which is not shown. Representatives of the Applicant company, Mahle International GmbH, presented technical descriptions of double camshafts that are described basically in DE 10 2005 014 680 A1 at the 16th Aachen Colloquium on Vehicle and Engine Technology 2007, showing figures and functional diagrams. As it was established at the colloquium, those skilled in the art have still not been able to successfully terminate their quest for suitable camshaft adjusters for appropriate double camshafts.
A camshaft adjuster for the relative rotating of a hollow camshaft and a second rotatable member disposed parallel to the first rotatable member is described in U.S. Pat. No. 6,253,719 B1 (Patent proprietor: Mechadyne PLC, Priority date: Feb. 18, 1999). Instead of arranging the two rotatable members with a type of disk structure next to one another, in the figures of U.S. Pat. No. 6,725,817 B2 (Patent proprietor: Mechadyne PLC, Priority date: Nov. 18, 2000), different embodiments of a nested adjuster lying in the same plane can be seen, whose first adjusting element can rotate a first set of cams of the concentric camshaft, while the second adjusting element is specific for the purpose of rotating a second set of cams of the concentric camshaft. In this way, the angular rotation of one set of cams influences the accessible angular region of the other set of cams. A similar presentation can also be taken from EP 1 234 954 A2 (Applicant: Mechadyne PLC, Priority date: Nov. 18, 2000). On the other hand, it would be more favorable if the sets of cams of the double camshaft could be adjusted as much as possible independently of one another in a further, larger adjustment range.
A type of connection for a double camshaft can be derived from EP 1 696 107 A1 (Applicant: Mechadyne PLC, Priority date: Feb. 23, 2005), in which both a camshaft adjuster as well as also an individual cam can be joined to the double-design camshaft by the use of cross-running pins. In this case, the pin is to be fitted with play in the crossbore of the camshaft.
The statement of the problem in U.S. Pat. No. 6,076,492 (Applicant: Yamaha Hatsudoki Kabushiki Kaisha, Priority date: Mar. 27, 1998) explains that in simply constructed camshaft adjusters of an axial displaceable type, there is a problem only in permanently aligning the camshaft adjuster, the cylinder head, the control valve and the camshaft in a stationary manner. Even for sufficiently known camshaft adjusters, there is a fear of jamming the individual components relative to one another.
Rotors with a broadened base are known from the publications DE 103 46 446 A1 and DE 103 46 448 A1 (Applicant: Daimler-Chrysler AG; Date filed: Oct. 7, 2003), the bases of which are fanned out opposite the vane width for reasons of stability or for conducting oil.
How camshaft adjusters can be connected to divided camshafts is shown in the drawings of DE 101 02 767 A1 (Applicant: Volkswagen AG; Date filed: Jan. 23, 2001). Each camshaft controls one type of gas-exchange valve. Thus, there is a camshaft adjuster for the gas inlet valves and a camshaft adjuster for the gas outlet valves. Each camshaft adjuster is disposed on the half of the camshaft belonging to it.
The presented embodiments of two gas-exchange valve actuation means that can be displaced or adjusted relative to one another in a control shaft are incorporated by their reference within the scope of the present description of invention, in order to increase the readability of the description of the invention in this way and thus to be able to emphasize the aspects of the present invention given below. The scope of their disclosure will be fully incorporated by their reference in the present description.
A gas-exchange valve control shaft, which is constructed from two camshafts that are disposed so that they engage in each other, preferably coaxially, the outer camshaft surrounding the inner camshaft, is also occasionally called a double camshaft. A double camshaft is a camshaft that is constructed in duplicate. Persons skilled in the art associate the term camshaft most frequently to a single shaft extending lengthwise on which all cams are disposed in a stationary manner relative to one another.
The problem to be solved by the present invention is to create a means by which a camshaft adjuster can be joined to a corresponding camshaft in order to operate the valve train of an internal combustion engine in a reliably flexible and optionally repeatedly exchangeable manner. Ideally, the camshaft adjuster can be adjusted or aligned to the camshaft during assembly. The individual groups of cams and the individual cams are to be reliably aligned to one another, to the remaining cams and groups of cams, particularly in the case of a double camshaft.